/******************************************************************************
 * Xen balloon driver - enables returning/claiming memory to/from Xen.
 *
 * Copyright (c) 2003, B Dragovic
 * Copyright (c) 2003-2004, M Williamson, K Fraser
 * Copyright (c) 2005 Dan M. Smith, IBM Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/mm_types.h>
#include <linux/init.h>
#include <linux/capability.h>

#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/balloon.h>
#include <xen/xenbus.h>
#include <xen/features.h>
#include <xen/page.h>

#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))

#define BALLOON_CLASS_NAME "xen_memory"

static struct device balloon_dev;

static int register_balloon(struct device *dev);

/* React to a change in the target key */
static void watch_target(struct xenbus_watch *watch,
                         const char *path, const char *token)
{
        unsigned long long new_target, static_max;
        int err;
        static bool watch_fired;
        static long target_diff;

        err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
        if (err != 1) {
                /* This is ok (for domain0 at least) - so just return */
                return;
        }

        /* The given memory/target value is in KiB, so it needs converting to
         * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
         */
        new_target >>= PAGE_SHIFT - 10;

        if (!watch_fired) {
                watch_fired = true;
                err = xenbus_scanf(XBT_NIL, "memory", "static-max", "%llu",
                                   &static_max);
                if (err != 1)
                        static_max = new_target;
                else
                        static_max >>= PAGE_SHIFT - 10;
                target_diff = xen_pv_domain() ? 0
                                : static_max - balloon_stats.target_pages;
        }

        balloon_set_new_target(new_target - target_diff);
}
static struct xenbus_watch target_watch = {
        .node = "memory/target",
        .callback = watch_target,
};


static int balloon_init_watcher(struct notifier_block *notifier,
                                unsigned long event,
                                void *data)
{
        int err;

        err = register_xenbus_watch(&target_watch);
        if (err)
                pr_err("Failed to set balloon watcher\n");

        return NOTIFY_DONE;
}

static struct notifier_block xenstore_notifier = {
        .notifier_call = balloon_init_watcher,
};

void xen_balloon_init(void)
{
        register_balloon(&balloon_dev);

        register_xen_selfballooning(&balloon_dev);

        register_xenstore_notifier(&xenstore_notifier);
}
EXPORT_SYMBOL_GPL(xen_balloon_init);

#define BALLOON_SHOW(name, format, args...)                             \
        static ssize_t show_##name(struct device *dev,                  \
                                   struct device_attribute *attr,       \
                                   char *buf)                           \
        {                                                               \
                return sprintf(buf, format, ##args);                    \
        }                                                               \
        static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)

BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));

static DEVICE_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
static DEVICE_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
static DEVICE_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
static DEVICE_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);

static ssize_t show_target_kb(struct device *dev, struct device_attribute *attr,
                              char *buf)
{
        return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
}

static ssize_t store_target_kb(struct device *dev,
                               struct device_attribute *attr,
                               const char *buf,
                               size_t count)
{
        char *endchar;
        unsigned long long target_bytes;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;

        balloon_set_new_target(target_bytes >> PAGE_SHIFT);

        return count;
}

static DEVICE_ATTR(target_kb, S_IRUGO | S_IWUSR,
                   show_target_kb, store_target_kb);


static ssize_t show_target(struct device *dev, struct device_attribute *attr,
                              char *buf)
{
        return sprintf(buf, "%llu\n",
                       (unsigned long long)balloon_stats.target_pages
                       << PAGE_SHIFT);
}

static ssize_t store_target(struct device *dev,
                            struct device_attribute *attr,
                            const char *buf,
                            size_t count)
{
        char *endchar;
        unsigned long long target_bytes;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        target_bytes = memparse(buf, &endchar);

        balloon_set_new_target(target_bytes >> PAGE_SHIFT);

        return count;
}

static DEVICE_ATTR(target, S_IRUGO | S_IWUSR,
                   show_target, store_target);


static struct attribute *balloon_attrs[] = {
        &dev_attr_target_kb.attr,
        &dev_attr_target.attr,
        &dev_attr_schedule_delay.attr.attr,
        &dev_attr_max_schedule_delay.attr.attr,
        &dev_attr_retry_count.attr.attr,
        &dev_attr_max_retry_count.attr.attr,
        NULL
};

static const struct attribute_group balloon_group = {
        .attrs = balloon_attrs
};

static struct attribute *balloon_info_attrs[] = {
        &dev_attr_current_kb.attr,
        &dev_attr_low_kb.attr,
        &dev_attr_high_kb.attr,
        NULL
};

static const struct attribute_group balloon_info_group = {
        .name = "info",
        .attrs = balloon_info_attrs
};

static const struct attribute_group *balloon_groups[] = {
        &balloon_group,
        &balloon_info_group,
        NULL
};

static struct bus_type balloon_subsys = {
        .name = BALLOON_CLASS_NAME,
        .dev_name = BALLOON_CLASS_NAME,
};

static int register_balloon(struct device *dev)
{
        int error;

        error = subsys_system_register(&balloon_subsys, NULL);
        if (error)
                return error;

        dev->id = 0;
        dev->bus = &balloon_subsys;
        dev->groups = balloon_groups;

        error = device_register(dev);
        if (error) {
                bus_unregister(&balloon_subsys);
                return error;
        }

        return 0;
}